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DFE World: Design & the Global Environment
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Air Pollution
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Exercises


Effective Stack Height
Mixing Height & Inversions
Model Output
Sensitivity Analysis

 

Central Campus Air Quality Model (CCAQM) Instructions

 

Effective Stack Height

Plumes rise vertically from a smokestack before starting to disperse according to the Gaussian model (see figure below).  Therefore, because of the plume rise, the centerline of the Gaussian model is higher than the height of the stack.  The “effective stack height”, which is stack height plus vertical plume rise, is used in the Gaussian model for more accurate calculations of pollution concentration from a point source.

 

 

 

 

 

 

Plume Rise and Effective Stack Height

 

 

Calculating Effective Stack Height Wind Speed

The surface wind speed is different at the effective stack height, which is used in the Gaussian model.  To determine the effective stack height wind speed, UH, use the following equation and table.

Where:

  • Ua = wind speed at altitude Za, m/s

  • H = effective stack height, m

  • Za= height above surface, m (usually 10 meters)

  • p = exponent is a function of atmospheric stability class

Stability Class

Description

Exponent p

A

Very unstable 0.15

B

Moderately unstable

0.15

C

Slightly unstable

0.20

D

Neutral 0.25

E

Slightly Stable 0.40

F

Stable 0.60